The present invention relates to a method of the type specified in the preamble of claim 1 and to a device of the type specified in claim 16 for measuring the quality of a network for the transmission of digital or analog signals, using an in-service non-intrusive measurement device monitoring of live traffic (INMD) measuring method.
Methods and devices for measuring the quality of a line network designed to transmit digital or analog signals, including the (terminal) connections which are used to connect telecommunication terminals such as telephones, fax machines, modems, mobile telephones or the like to the line network, are generally known.
Thus, for example, the INMD measurement method (in-service non-intrusive measurement device monitoring of live traffic) exists which works according to ITU-T standard P.561 and the further development thereof. Using this measurement method, parameters describing the quality of the transmission can be queried during operation, for example, during a telephone conversation. Possible parameters of the measurement method can includes the speech level, the noise level, the echo delay time, the active return loss or the like in the payload channel.
Moreover, it is also possible to acquire the information of the signaling channel such as the D-channel or the central signaling channel No. 7 (SS No. 7).
This measurement method has the advantage of permitting information on the change in individual parameters over a predetermined time in the line network without intervention in the line network, i.e., without disconnection of parts of the line network. In this manner, the INMD method can detect potential anomalies such as periodically occurring noise, echo problems at line terminating units, etc. from the environment of terminal devices and between the interfaces of network elements.
However, the values determined for the individual measuring parameters are meaningful only with respect to their change over time. For instance, the speech level changes during the duration of a telephone conversation or, at a specific instant of another measurement, the noise level was different from that of this measurement. It is then possible to draw conclusions from this and to take measures by which the causes of the changes in the measurement parameter and, thus, the quality limitation of the transmission are eliminated.
However, this known measurement method has the disadvantage that it is not possible to specifically isolate the error to the actual cause of the quality impairment of the transmission in the line network or to exactly locate the errors. Moreover, parameters are measured which are influenced by the telecommunication terminal as well. Therefore, the explanatory power with respect to the possible quality in the line network is insufficient.
Moreover, there is basically one measurement method which is known as “out of service, intrusive network” measurement method and works according to ITU-T standard P.861. In this case, both telecommunication terminals and elements of the line network have to be disconnected from the line network to determine transmission characteristics at selected points of the line network. Then, an RTU (remote test unit) is connected at the separation points such as connections or distributors. This RTU serves as a transmitter at one end and as a receiver at the other end. The RTU is a test device which simulates functions of terminal devices, i.e., the transmission of speech information, data, image information and the like. Using predetermined parameters, different physical quality considerations can be performed out of service in the network from the transmitter to the receiver which constitutes the measuring point. It is also conceivable to integrate the RTU functions as a remotely controllable module or chip into a terminal device (for example, use in a Multimedia Internet PC).
However, this measurement method has the disadvantage that the real situation during the transmission of analog or digital signals, for example, during telecommunication (live traffic) between a customer A and a customer B cannot be monitored. Consequently, neither influences of the telecommunication terminals on the line network nor repercussions from the line network to the telecommunication terminals can be detected immediately. Furthermore, the expenditure, in particular the personnel expenditure, for this measurement method is very high.
Also known is a network planning model, the so-called “E-model” according to ITU standard G.107, which permits calculation of the transmission quality.